1. Field of the Invention
This invention relates generally to hand-held dispensers, and more particularly to dispensers of the type having a base cap part that is applied to a container, and an overcap or twist cap applied to the base cap, and wherein discharge of the container contents is controlled by manually turning the twist cap between an open, discharging position and a closed, sealing position.
2. Description of the Related Art Including Information Discussed Under 37 CFR SS1.97-1.99
One prior twist cap construction is illustrated and described in my U.S. Pat. No. 4,424,918, and relates to a non-resealable dispenser construction. A twist or cover cap is turnably carried on a base cap in such a manner that when the cover cap is initially unscrewed, a shoulder on the latter is received in a groove on the base cap and the resulting interference therebetween prevents the twist cap from being pushed down and re-seated on the base cap. Inadvertent build-up of pressure in the dispenser is thus prevented, following initial use.
This patented dispenser incorporated no means for controlling the flow of product being discharged. The rate of discharge was determined by the size of the openings on opposite sides of the stopper peg, and the viscosity of the liquid.
U.S. Pat. No. 4,438,870 shows a different construction wherein a twist cap is raised by cam lugs carried on its underside and which engage cam tracks on a base cap, and is retracted by cooperable threads on both the twist and base caps. While this construction was capable of providing an adjustable flow, control was difficult to set or calibrate, since it depended for the most part on the relatively sudden removal of the stopper peg from the orifice in the twist cap. In actuality, the control was more in the nature of a simple "on-off" type of control, rather than one providing continuous adjustment over a reasonably well defined range.
Thus, the capability of providing a simple and foolproof high precision adjustable discharge function in a twist cap was not provided in any of the devices disclosed in the patents listed above.
A number of other twist cap constructions have been proposed and produced. It is believed that the above identified two patents constitute the closest prior art of which applicant is aware.